The Collaborative International Dictionary of English v.0.48:

Addison's disease \Ad"di*son's dis*ease"\ [Named from Thomas
   Addison, M. D., of London, who first described it.] (Med.)
   A morbid condition causing a peculiar brownish discoloration
   of the skin, hypotension, and loss of weight; it is due to
   insufficient secretion of adrenocortical hormones. Untreated
   disease is usually fatal. Called also chronic adrenocortical
   insufficiency
   [1913 Webster + AS]